Fatty acids are important commercial materials and find uses in a myriad of applications. For example, fatty acids may be incorporated into ore flotation compositions (see, e.g., U.S. Pat. Nos. 6,149,013 and 6,133,474); and surfactant compositions (see, e.g., U.S. Pat. No. 6,126,757). In addition, fatty acids are reacted with various chemicals to provide a diverse range of commercially useful materials, e.g., reaction with polyfunctional materials to provide polymers, e.g., reaction with polybasic acids and polyhydric alcohols to provide an alkyd resin (see, e.g., U.S. Pat. Nos. 6,262,149 and 6,127,490); reaction with polyethyleneamines provides polyamidoamines useful in, e.g., epoxy curing agents (see, e.g., U.S. Pat. No. 6,258,920); reaction with diethanolamine provides diethanolamides useful as, e.g., biocides (see, e.g., U.S. Pat. No. 6,235,299); reaction with polyamines provides intermediates in the formation of corrosion inhibitors (see, e.g., U.S. Pat. No. 6,063,334). This list presents a small fraction of the many commercial uses wherein fatty acids are employed.
The successful handling of fatty acids is therefore an important process. A problem with the handling of fatty acids is that they often do not have satisfactory low temperature handling stability. Handling stability at low temperature is important because the transport and storage of fatty acids often occurs at low temperature, e.g., at less than 25° C., and often at less than 0° C.
Fatty acid as used in many commercial processes is typically a blend of fatty acid structures. The handling instability often observed at low temperatures manifests itself in the precipitation of some or all of the components of the fatty acids. The precipitation of fatty acid components at low temperature is a problem in many instances. For example, when fatty acid is taken from a storage tank to a reaction vessel, it is typically pumped from the storage tank. When components of the fatty acids have precipitated and settled to the bottom of the storage tank, that precipitate is not readily pumped from the tank. Typically, the composition of the precipitated fatty acids is not identical to the composition of the fatty acids as a whole, and therefore the composition of fatty acids that is pumped from a tank containing precipitated fatty acids depends on the temperature of the storage tank. The composition of the fatty acids may, and often does impact the reactivity and performance properties of the fatty acids. Industrial users of fatty acids do not want to have to worry about the temperature of the storage tank when they pull fatty acids from the tank to the reaction vessel.
In addition, a transport tank that contains a mixture of liquid and precipitated fatty acids is obviously more difficult to completely empty than is a tank containing a homogenous fluid mixture of fatty acids. The formation of precipitate can render the discharge process from a storage or transport tank very difficult. Thus, even if the fatty acid is a single component, the formation of crystals within the fatty acids can pose problems to the commercial user.
Maintaining a homogeneous fluid mixture of fatty acids, even at low temperature, is a problem that has previously received some attention. One solution is to provide a heating source to the storage or transport tank. This heating source can be used to maintain, or achieve, a temperature within the tank at which precipitation is not observed. A shortcoming with this particular approach is that heating sources are expensive to install, use, and maintain.
A different solution is to add some solvent to the fatty acid, and in particular a solvent that will dissolve precipitated or crystallizing fatty acid as it forms, thus maintaining a homogeneous solution. A problem with this approach is that a supply of solvent must be maintained, which adds expense and complication to the use of the fatty acids. In addition, the presence of solvent in the fatty acids will impact the “acid number” of the composition, i.e., the number of moles of carboxylic acid groups that are provided by a gram of the composition. Typically, commercial users employ sufficient amount of fatty acid to provide a desired amount of carboxylic acid groups. When the composition contains non-acidic solvent, then the acid number of the composition is less than the acid number of fatty acid alone. The presence of solvent therefore requires the operators of a reaction vessel to be concerned about the concentration of solvent in the fatty acids. As reaction vessel operators already have a lot to be concerned with, the addition of this complication is not welcomed by such operators.
The present invention provides a new solution to this problem, which overcomes the problems associated with those solutions that have been suggested in the past.